Ask any fans of The Big Bang Theory about the brilliant Dr. Sheldon Cooper’s greatest struggle and they’ll quickly respond with “understanding other people.” More specifically, Sheldon confesses to having an immensely difficult time interpreting others’ emotions (like sadness or disappointment) and responding empathically. And—played out to great comic effect on the show—he seems completely unable to decode others’ sarcasm. (At one point, his friend and roommate, Leonard, has to hold up a sign that says “SARCASM” to help Sheldon navigate a particularly intense conversation with their neighbor, Penny!)

Truth be told, Sheldon struggles to interpret and understand nonverbal codes, the symbols we use to send messages without, or in addition to, words. Although we divide these codes into categories for simplicity and clarity, nonverbal behaviors seldom communicate meaning in isolation; as you saw in the last section, clusters of nonverbal behaviors (hugs, smiles, eye contact) function together to regulate behavior or convey immediacy. The codes we examine here are gestures and body movements, facial expressions, eye behavior, voice, physical appearance, space and environment, touch, and time.